2. Readout of Higher-level Processing in the Discharge of Superior Colliculus Cells Edward L. Keller, Kyoung-Min Lee and Robert M. McPeek The Smith-Kettlewell Eye Research Institute San Francisco, CA and Seoul National University, Seoul, Korea

3. Delayed-saccade paradigm Fixation point Target Eye Delay

5. From Basso and Wurtz 1998: Correlation with prior probability

6. Visual Search Task

8. Search: Target in Field Single Target Search: Distractor in Field Delayed Saccade: Target in Field Second burst Time from stimulus onset (ms)

9. Search: Target in Field Search: Distractor in Field Earliest Discrimination Threshold Area Under ROC Curve

14. 33 ga. Injection cannula with attached micro-electrode Location on SC map determined by recording and stimulation Injected Lidocaine (2%; 0.25 - 1.25 ul) or muscimol (0.5 ug/ul; 0.25 - 1 ul) Test target selection and motor execution pre-injection, post-injection, and after recovery

19. Time Targets Masks Cue Choice response task

20. Two choice response task

21. Fixation point Cue 4 4 RF

25. Conclusions Most neurons in the deeper layers of the SC show activity aligned with the visual input and the motor response in single-target tasks. Many of these same neurons show additional discharge that is correlated with higher- level decision processes in more natural visual tasks. In the case of pop-out search the SC has been shown to be functionally involved in the decision processes. The cue aligned activity in SC in the choice response task is surprising because no transient visual stimulus appeared in the response field of the neuron. It remains to show whether this cue aligned activity is functionally related to choice response.